Several surgical procedures have been developed in recent years which are intended to clear obstructions from the arteries of a patient so that the normal flow of blood through the patient can be restored. These obstructions, sometimes also referred to as lesions or stenotic segments, can cause very considerable difficulties for the patient. Consequently, they should be removed or cleared at the earliest convenience, if not immediately.
Presently, there are primarily two quite different procedures which are used for clearing an obstruction in an artery. One is an atherectomy procedure wherein the plaque which is causing the obstruction is cut and actually removed from the artery. An example of such a procedure is disclosed in U.S. Pat. No. 4,887,613 for an invention entitled "Cutter for Atherectomy Device" which is assigned to the assignee of the present invention. The other is an angioplasty procedure wherein the plaque is pushed aside by an expanding balloon to dilate the artery. The present invention is more concerned with this later type procedure, i.e. an angioplasty procedure.
As might be expected, the plaque which builds up in an artery to eventually obstruct the flow of blood through the artery can have significantly different consistencies. Sometimes the plaque is relatively soft and can be fairly easily deformed. Plaque of this nature has been likened somewhat to cheddar cheese. In other cases, the plaque can be relatively hard or brittle and can even be somewhat fibrous in nature. In this later case, the plaque is not so easily deformed. Moreover, the plaque in any given stenotic segment will most likely not be homogenous and will include plaque having several different consistencies. The consequence is that it is not uncommon for an obstruction to be, at least partially, composed of the more hard and brittle plaque which is not so easily deformed. Unfortunately, the ability to deform the plaque in an obstruction, and to thereby dilate the artery, is of utmost importance for the efficacy of an angioplasty procedure. Thus, in order to improve the expected results of an angioplasty procedure, and particularly in those cases where the plaque may put up stiff resistance there is a need to properly prepare the obstruction for subsequent dilatation of the artery.
In light of the above, it is an object of the present invention to provide an expandable endarterectomy cutting tool for incising stenotic tissue in an artery which will weaken plaque in a stenotic segment and thereby facilitate a subsequent angioplasty procedure. Another object of the present invention is to provide an expandable endarterectomy cutting tool for incising stenotic tissue in a predictable manner which efficiently promotes dilatation of the stenotic segment. Still another object of the present invention is to provide an expandable endarterectomy cutting tool for incising stenotic tissue in an artery which is safe to use. Another object of the present invention is to provide an expandable endarterectomy cutting tool for incising stenotic tissue in an artery which has a cutting tool that provides positive expansion and contraction of its cutting blades. Yet another object of the present invention is to provide an expandable endarterectomy cutting tool for incising stenotic tissue in an artery which is relative simple to manufacture, easy to use, and comparatively cost effective.